1. Field of the Invention
The present invention relates to a data copying system, a data copying apparatus, a data copying method and a recording medium for copying digital data such as music data with a copyright protection function.
2. Description of the Related Art
Conventionally, high quality video and sound data has been recorded/reproduced by using a special apparatus for digitally recording/reproducing video and sound data to/from a recording medium. Media for recording digital data include a laser disk (LD), a compact disk (CD), a mini disk (MD) and a digital versatile disk (DVD).
Such a digital data recording medium, unlike an analog data recording medium such as a (compact) cassette tape and a VHS tape, is characterized in that the quality of the recorded data is less likely to degrade through copying. In other words, it is easier for digital data than analog data to be accurately recorded/reproduced. The quality of digital data never degrades as long as data that is identical to the digital data stored in an original recording medium is written to a duplicate recording medium.
However, a user of an apparatus for record-ing/reproducing a digital data recording medium may duplicate a commercially sold recording medium in which video data, music data, or the like, is recorded, thereby infringing the copyright of the copyright holder of the recorded data. In view of this, such an apparatus for recording/reproducing a digital data recording medium is provided with a function to restrict copying of a recording medium. For example, when music data is copied from a CD to an MD, the apparatus degrades the quality of the music data, thereby restricting such copying and thus protecting the copyright on the music data.
However, if the apparatus in designed to always degrade the sound quality of music data being copied, music data cannot be copied with high quality even when copying of the music data is permitted by the copyright holder. For example, the copyright holder of the music data may desire to selectively permit a user to duplicate the music data depending upon whether the user has paid the copyright holder the royalty for the music data. The copyright holder of the music data may also desire to permit the high quality copying of the music data free of charge.
With the conventional copying system, it is not possible to set different royalties for different sound quality levels at which copying is to be permitted so as to allow the user to select a sound quality level to the user's preference. Therefore, the sound quality level of copied music data may not meet the user's preference.
In order to solve the above-described problem, copying of data may be permitted on the condition that the royalty therefor has been paid. In such a case, it is necessary to prevent a “pirate” (a person who illegally copies data such as music data) from copying the data without paying the royalty.